Most consumers have come to expect scented laundry products and to expect that fabrics which have been laundered to also have a pleasing fragrance. It is also desired by consumers for laundered fabric to maintain the pleasing fragrance over time. Perfume additives make laundry compositions more aesthetically pleasing to the consumer, and in some cases the perfume imparts a pleasant fragrace to fabrics treated therewith. However, the amount of perfume carry-over from an aqueous laundry bath onto fabrics is often marginal and does not last long on the fabric. In addition, some perfum delivery systems are not stable under alkaline conditions, such as in laundry detergent compositions. Fragrance materials are often very costly and their inefficient use in detergents and ineffective delivery to fabrics from detergents results in a very high cost to both consumers and detergent manufacturers. Industry, therefore, continues to seek with urgency for more efficient and effective fragrance delivery in laundry products, especially for improvement in the provision of long-lasting fragrance to the lundered fabrics.
Acetals and ketals have long been known in perfumery. See Steffen Arctander, "Perfume and Flavor Chemicals", Arctander, N. J., 1969. The majority of these are methyl and ethyl types, and molecular weights may range widely. See, for example, Arctander abstract numbers 6, 11, 210, 651, 689, 1697, 1702, 2480, 2478. For 2478, which is phenylacetaldehyde dicitronellyl acetal, molecular weight 414.7, Arctander reports " . . . and it is not exaggerated to say that this acetal is practically abandoned and obsolete in today's perfumery". For 2480, which is phenylacetaldehyde digeranyl acetal, Arctander reports "the title material does not offer substantial advantages or unique odor type and it may be considered of little more than academic interest today". This latter material was still commercially available in 1992 as ROSETAL A (Catalogue, IFF). The present inventors have found indeed that the acetals of aldehydes which have low molecular weight and contain a C.sub.6 H.sub.5 moiety, such as benzaldehyde and phenylacetaldehyde, do not have very desirable odor character for use in a pro-fragrancing detergent mode. Yet another group of commercial acetals sold for incorporation in perfumes are those of undecylenic aldehyde, such as the digeranyl or dicitronellyl acetals. The present inventors have found that these materials too are not very desirable for use in profragrancing detergent compositions.
Carrier mechanisms for perfume delivery, such as by encapsulation, have been taught in the prior art. See for example, U.S. Pat. No. 5,188,753.
Early efforts to delay release of perfumes in detergents include the use of certain organometallic compounds, such as titanate or zirconate esters. See U.S. Pat. No. 3,849,326, Jaggers et al, issued Nov. 19, 1974 and U.S. Pat. No. 3,923,700, Jaggers et al, issued Dec. 2, 1975. Limited amounts of titanium or zirconium can be useful as catalysts for synthesizing pro-fragrant materials herein, and may be present in minor amounts in comparison to the present invention; however, organometallic titanium or zirconium compounds, or the metals per se, are not essential components of the pro-fragrant materials herein.
U.S. Pat. No. 5,378,468, Suffis et al, issued Jan. 3, 1995 describes specific types of personal care compositions, such as deodorant sticks, comprising assertedly "body-activated" fragrances. The term apparently refers to the previously known tendency of materials such as acetals derived from fragrance alcohols to hydrolyze under acidic pH conditions thereby releasing fragrance. See, for example, U.S. Pat. No. 3,932,520, Hoffman, issued Jan. 13, 1976.
Factors affecting substantivity of fragrance materials on fabrics are discussed in Estcher et al. JAOCS 71 p. 31-40 (1994).
The selected potential fragrance materials described by Suffis et al include particular acetals and ketals, exemplified by propylene glycol vanillin acetal. The materials exemplified apparently are rather bydrophilic short chain alcohol or diol derivatives of fragrance aldehydes and upon hydrolysis, deliver one mole of the aldehyde per mole of the potential fragrance material. The present inventors believe that hydrophilic acetal or ketal materials, i.e., those having a CLogP value (described hereafter) of less than 4 have at best limited usefulness in laundry detergent compositions. The Suffis et al development is designed to be incorporated with a personal care product vehicle, resulting in clear deodorant sticks and the like.
For detergent use, it is important that rather hydrophobic pro-fragrant compounds be used in order to enhance deposition onto surfaces in the wash solution and retention on the washed surface during rinsing. In Suffis et al, the compositions containing the potential fragrance materials are applied directly to the substrate (i.e. skin); therefore, the deposition problems resulting from dilution, rinsing, etc. are not at issue.
More specifically, in contrast to deodorant sticks and the like, laundry detergents are used in dilute aqueous form and contain numerous detergent adjuncts such as synthetic detergents, builders, enzymes and the like which are capable of micellizing, or solubilizing the pro-fragrance. Further, in order to remove detergent adjuncts and the soils displaced by detergent adjuncts from the fabrics, the latter are rinsed after washing. The rinsing tends to remove the useful pro-fragrance material deposited. Thus both the detergent adjuncts and the essential steps of the wash process itself all work against the effective delivery of pro-fragrances to the fabrics being washed. Moreover, high-efficiency pro-fragrant systems are desired for laundry purposes. In many laundry applications, the use of heated tumble-drying appliances further exacerbates the problem of delivering adequate residual fragrance to textile fabric surfaces. Suffis et al are silent on both the nature of these severe technical problems and shortcomings, as well as methods and specific pro-fragrances to overcome them.
It has now surprisingly been discovered that these problems can unexpectedly be overcome by the selection of specific organic pro-fragrance types. Moreover, when these pro-fragrance types are selected, a simple but effective method is successfully provided for their effective delivery. Accordingly, objects of the present invention include the provision of such pro-fragrance types and the corresponding detergent compositions and methods. While the present invention is primarily directed to the laundering of fabrics, the compositions of the present invention are also useful in the washing of other surfaces (e.g. hard surfaces such as floors, walls, and dishes) when it is desired to impart residual fragrances to the washed surface.
By the term "pro-fragrance" herein, it is meant a compound which may or may not be odoriferous in itself but which, upon hydrolysis, produces a desirable odor which is characteristic of one or more of its hydrolysis products. Of course. mixtures of pro-fragrance compounds can also be considered a pro-fragrance.